There are known systems for transmitting fluids in a manner that minimize fluid loss during transmission. For example, mechanical shaft seals have been employed around the rotating shaft of a pump to seal the interior of a pump from the exterior. However, pumping dangerous liquids where seals are employed usually presents both a safety and a maintenance concern because of the propensity for these mechanical seals to break down resulting in material, often toxic to humans, being lost from the system. Pumping slurry-containing liquids enhances these concerns because the abrasive qualities of these slurry-containing liquids usually aggravate the propensity for seal breakdown.
Another system for transmitting fluids while minimizing fluid loss is by the use of canned motor pumps. Canned motor pumps are constructed such that the pump and the motor are formed integrally. The impeller of the pump and the rotor of the electric motor for operating the pump actually rotates while the entire motor and pump assembly is immersed within the fluid to be transmitted. Canned motor pumps have no packing glands, and a seal is provided to the pumped fluid solely by means of gaskets. Canned motor pumps, because of their location within the vessel containing the fluid to be transmitted, can be made essentially leak-proof. Since the rotary bearing portion of these canned motor pumps is usually lubricated by the transmitted fluid itself, the handling of liquids of the type described above, especially slurry-containing liquids, will cause abnormal wear of the bearing and shaft which will inevitably require the cessation of operation of the pump.
Magnet driven pumps have been suggested for transmitting these special fluids but their reliability is low. These special pumping problems are further aggravated and compounded when the fluids to be transmitted are under pressure. Fluid will usually be ejected under pressure from holes that develop in the system.
Vertical pumps, i.e. pumps whose shaft are maintained in a vertical position, are normally installed external to a storage vessel to be evacuated and have been used to pump special fluids when they are not being stored under pressure. However, there is no known external pumping system for safely and effectively pumping a slurry-containing liquid or a dangerous liquid both of which are under pressure. High pressure pumps for handling even ordinarily harmless liquids have been found to be prone to leakage, especially at their seal location.
Although various attempts have been made to overcome the problem inherent in pumping slurry-containing liquids and dangerous chemicals, all being under pressure, no completely satisfactory solution has been found prior to the present invention.
The present invention overcomes the problems of the prior art and provides an apparatus which employs a vertical pump in a manner which is safer and more effective than heretofore known. The present apparatus provides means for substantially or completely eliminating fluid loss through seal leakage in a vertical pump while pumping slurry-containing liquids and dangerous chemicals all being under pressure. The present apparatus further permits the vertical pump to be automatically isolated when seal leakage occurs so that the spills that usually accompany these leaks can be reduced or completely eliminated.